This invention relates generally to a flange seal assembly and more particularly to a flange seal assembly utilized with multi-layered plastic fuel tanks.
Environmental concerns and regulations have spurred the need to reduce the amount of hydrocarbon fuel vapors emitted by vehicles and have led to the development of new technologies for manufacturing plastic fuel tanks. A fuel tank constructed from a single layer of a plastic, such as high-density polyethylene, has been found to have an unacceptably high permeation rate of fuel vapor emission. Therefore, current plastic fuel tanks are formed with multiple layers, one of which is a fuel vapor permeation barrier layer.
Flange connections required to mate with holes in the fuel tank are typically secured to the pre-molded tank by welding. Resilient seals, applied within the flange, typically contact the outer layer of the tank and do not seal directly to the permeation barrier layer. Consequently, permeation and vapor emission occurs about the flange area of the fuel tank.
A flange seal assembly seals against vapor permeation through fuel tank wall portions which surround an opening through a multi-layered plastic fuel tank. The plastic fuel tank has a permeation barrier layer preferably encapsulated by a outer layer and a inner layer. The permeation barrier layer is required to prevent the permeation and subsequent release of hydrocarbon and alcohol fuel vapors from the fuel tank. To further prevent the release of fuel vapor, the permeation barrier layer is preferably in contact with a permeation resistant seal located within the flange seal assembly. The flange seal assembly further comprises a ring and preferably a locking member, both of which envelop the hole in the fuel tank wall.
The fuel tank wall is blow molded about the ring. The ring preferably has a sleeve rigidly secured to a radial shelf encapsulated by the outer layer and preferably provides vertical support for a channel which receives the seal. The shelf extends radially inward from the sleeve and the sleeve extends axially upward from the shelf. The sleeve preferably has a plurality of tabs releasably engaging the locking member and a plurality of datum members used during blow molding and circumferentially around the channel. The tabs and the datum members extend intermittently around the hole, outward of the channel, and are exposed above the outer layer of the fuel tank wall.
Preferably, the locking member has a plurality of apertures each of which receives a tab of the sleeve and upon rotation engages a slot in each tab to secure them together. When the locking member is engaged within the slots, it applies a normal force exerted down upon a flange to compress the seal. The flange, in turn, exerts a force upon the seal which mates between the flange and the wall and into sealing engagement with them and preferably the permeation barrier layer.
Objects, features and advantages of this invention include a seal assembly which prevents fuel vapor loss from permeation, liquid fuel loss from seal leakage, is of relatively simple design, economical to manufacture and assemble, and has a long useful service life.